Due to advantages of the large band gap, high electron mobility, high breakdown field strength and high temperature resistance, GaN semiconductor devices are suitable for manufacture of electronic devices with high temperatures, high voltages, high frequencies and high powers, and thus have broad application prospects.
FIG. 1 is a schematic top view illustrating a gallium nitride semiconductor device of the prior art. Referring to FIG. 1, a gallium nitride semiconductor device of the prior art comprises an active region a′ which is an enclosed area and a passive region b′ which is located outside the active region a′. Source electrodes 11′, drain electrodes 12′ and gate electrodes 13′ located in the active region a′ are repeatedly arranged in a width direction of the device, so as to form a multi-finger structure. The whole semiconductor device is rectangular in plan view. The repeatedly arranged drain electrodes 12′ are connected together through a drain interconnection metal 14′ located in the passive region b′, the repeatedly arranged gate electrodes 13′ are connected together through a gate interconnection metal 131′, and the semiconductor device receives signals from the outside through lead pads 15′.
The gallium nitride semiconductor device has a very high power density, thus has a very high heat density, so that a large amount of heat is generated during operation of the gallium nitride semiconductor device. If the generated heat cannot be dissipated in time, an internal temperature of the gallium nitride semiconductor device will rise, which affects stability and reliability of the device and limits an output power of the device. In addition, in the gallium nitride semiconductor device of the prior art, the active region a′ occupies the most area of the device, thus it is difficult to promptly transfer heat generated in a central region of the gallium nitride semiconductor device through lateral paths, while the thermal conductivity through longitudinal paths is saturated. Therefore, the gallium nitride semiconductor device will have a relatively high temperature in the central region and a relatively low temperature in its edges, i.e., there is a nonuniform temperature distribution, which degrades performances of the gallium nitride semiconductor device and reduces the reliability thereof.
FIG. 2 is a schematic top view illustrating a gallium nitride semiconductor device of the prior art with an increased heat dissipation area. Referring to FIG. 2, a gallium nitride semiconductor device has an increased space between gate electrodes 13′. By increasing a width of the whole gallium nitride semiconductor device to increase the heat dissipation area, heat dissipation is improved. However, the whole gallium nitride semiconductor device is very wide and thus has a large width-length ratio, which results in some disadvantages such as increased difficulty in the subsequent processes such as cutting and packaging etc., decreased yield and reduced performances such as increased gate resistance or desynchronized radio-frequency signal phases. Furthermore, it is still difficult to dissipate heat generated in the central region of the gallium nitride semiconductor device, the device still has a relatively high temperature in the central region and a relatively low temperature in its edges, that is, the temperature distribution is still not uniform.